1. Field of the Invention
The present invention relates to an electrostatic discharge (ESD) device, and more particularly, to an ESD device with parasitic silicon controlled rectifier (SCR) structure and controllable holding current.
2. Description of the Related Art
ESD devices are widely applied in integrated circuits (IC) for preventing damage caused by static electricity. However, a latch-up effect inevitably exists since the inherent characteristics of the parasitic SCR structure of the ESD device. When the SCR structure is triggered, the ESD device can endure high currents. However, the voltage across the SCR would snap back to a low-holding voltage, which causes the latch-up effect. As the SCR structure is latched up, the ESD device cannot return to the normal operation state and fails to function normally.
How to improve the latch-up immunity of the ESD device has become a major issue in designing the ESD device nowadays. Accordingly, an ESD device having controllable holding current to improve the latch-up immunity is especially desired.